Process for the elimination of aluminum and metals of the iron group from zinc, zinc alloys, etc.



Patented Nov. 11,1924.

STATES PATENT Fim- KARL BORNEMANN, 0F BRESLAU, GERllLIANY, ASSIGNOR ONE-HALF TO ERICK A. BECK, OF 'NEW YORK, N. Y.; MARTHA BO'RNEMANN ADMINISTRATRIX OF SAID I KARL BORNEMANN, DECEASED.

PROCESS FOR THE ELIMINATION OF ALUMINUM AND METALS OF Elli-IE IRON GROUP FROM ZINC, ZINC ALLOYS, ETC. f v

No Drawing.

, vanizing baths, zinc dross and residues containing metallic zinc, from which ity is de-' sired to remove the content of aluminum or metals of the iron group or both.

It is well known that various iron-aluminum alloys have relatively high melting points, and, upon cooling from a molten condition,'assume a crystalline structure. The different iron aluminum alloys are also capable of forming mixed crystals with each other. The most important of the iron aluminum alloys is the one corresponding to the formula FeAl These mixed crystals will hereinafter be briefly referred to as compounds. What has above been said in regard to the alloys of iron with aluminum applies also to the alloys of the other metals of the iron group with aluminum, and in the present specification, for the sake of simplicity I will refer to ironaluminum alloys, as being substantially the same as alloys of the iron group metals with aluminum. I have found that it is possible to form the alloys of iron and aluminum even in the presence of a large quantity of metallic zinc, and I have further found that upon cooling the liquid mixture containing iron aluminum alloy and Zinc to just above the melting point of zinc', the iron aluminum alloy will readily crystallize, and the crystals being much ighter than the -molten zinc will rise in the bath and 'float upon the surface thereof, and can be readily removed therefrom by a simple operation, 'such as skimming, or the molten zinc. can be drawn away from below the surface, leaving the.

iron aluminum alloy inthe receptacle. It

take place.

Application filed May 20,1922. SeriaLNo. 562,470.

' is thus seen that the alloyof iron and aluration of the alloy from the zinc or from the major portion of the zinc can readily be effected. At temperatures slightly above the melting point of zinc, the iron aluminum alloys are practicall insoluble in molten "zinc, although at, hig er temperatures, they dissolve with some difliculty in metallic zinc. This principle for the separation of either iron or aluminum or both from the metal zinc, is accordingly applicable so long as a sufiicient amount of zinc is present to form a molten bath in which the solid alloy of aluminum and iron can float.

It is also surprising that other metals, which are often present in alloys with a high zinc content, such as copper and tin, also lead which is practically always pres-- ent, behave substantially the same as the zinc and hence will not in any Wayinter- -fere with the operation of the process.

The process is practically carried out, starting with zinc or an alloy of zinc containing aluminum or metals of the. iron group. Alloys containing zinc and aluminum can be. melted, and can be added to molten alloys containing zinc and iron. The

charge is then well-mixed,and if at a temperature below 600 to 800 C., is preferably heated to that temperature or at least up to 500 (3., in order to allow the combination between the iron and aluminum to readily The bath is then cooled down nearly to the melting point of zinc, and is then-allowed to stand quietly for a short time, say an hour or so, during which time the iron and aluminum alloy solidifies into crystals which have risen to the surface of the bath. The crystals may then be separated from the bath, for example, by means of skimming.-. As an alternative way of proceeding, the aluminum zincalloy can be added to molten zinc iron alloy, or if desired a charge containing all-three of the metals, aluminum, iron and zinc" can be melted, and then treated in the manner above described.

It is immaterial what mode of heating is employed, a 'reverberatory, a crucible or a kettle can be used, this preferably being lintlad on the inside with a refractory materla When it is desired to remove the iron'or aluminum or both, to a very complete degree, the process can be repeated one or more times. If it is desired to remove the aluminum very completely a slight excess of iron can be used, and this excess will then settle out in the bottom of the bath in the form of zinc iron alloy, as crystals, which crystals can subsequently be utilized in the treatment of further quantities of alloys containing .zinc and aluminum. In this mode of working, an excess of iron is added to the alloy, the bath heated up to the temperatures above stated, and this allowed to cool to slightly above the melting point of zinc, and allowed to stand quietly until the iron aluminum alloy has risen to the top and the iron zinc alloy has settled to the bottom, after which the three layers, namely, the iron aluminum alloy, the metallic zinc and the zinc iron alloy can girfeadily be separated from each other. 1

An imPPll-R itapplication of the process is its application in the treatment of galvanizing baths, which contain an alloy of zinc and iron. These baths may be treated with aluminum, from time to time, and the alloy'of iron and aluminum separated, for example, by sklmming. In this process it is advisable to heat the bath before or after the addition.

of the aluminum up to about 500 (3., then allow the bath to cool .to justabove the melting point of zinc, after which the crystals which have risen to'the surface are removed. The working up of the residue of the process does not entail any serious clifliculties. Obviously in removing the iron aluminum crystals there will ordinarily be removed some metal zinc therewith. Ithas been shown that from this material, the zinc content can be distilled oflz' in asimple manner, for instance by immersing the-alloy into a bath of liquid iron, and the'remaining iron aluminum compound can then be employed for the production of ferro-aluminum as a saleable product. Instead of a-bath of molten iron, obviously a bath ofother metal of the iron group could be similarly employed. In carrying out the process, it is usually advisable to hold'the bath at about 450 to 500 0., for some time, say about three hours, in order to allow the crystals of iron-aluminum alloy to rise to the top, and to then separateat about 500 C. This may be accomplished by allowing the. crucible containing the mass -to spontaneously; cool, from 600 5 C. to a temperature slightly above the melting point of zinc, during about six hours, and then skimming or tapping.

What I claim is: 1. The method of recovering metallic zinc from admixture with a metal of the iron cup and aluminum, which comprises sub-' )ecting the mixture to a temperature of at least 500 (3., then coolingto slightly above the melting point of zinc and thereafter separating the bulk of the solid alloy of aluminum with the metal of the iron group and the bulk of the molten zinc from each other. 2. The method of recovering metallic zinc from admixture with at least one constituent of an iron-aluminum alloy, which comprises adding the constituent of such latter alloy in which the mass is deficient, maintaining the mass at a temperature not below 500 C. until the iron and aluminum have combined to form a high melting point alloy, cooling to a little above the melting point of the least of solidified iron-aluminum alloy and Y the major part at least of the zinc from each other.

e. In the method of claims, the step 01:

adding the component of the iron-aluminum alloy in which the original material is deficient in the form of an alloywith zinc.

4. The method of removing aluminum and iron-group metal from materials containing metallic zlnc which comprises adding to the molten zinc containing anexcess of one of the constitutents of iron-group-aluminum alloy a material containing the other constituents of such alloy, maintaining the molten mass at a temperature sufiicient to effect'combinationof the iron group metal and aluminum, and thereafter separating the alloy of aluminum and iron-group metal, and the zinc from each other.

5-. The method of removing aluminum and iron-group metal from materials containing metallic zinc which comprises adding to the molten zinc containing an excess of one of the constituents of iron-group-aluminum a1- loy a material containing the other constitfuent of such alloy, heating themixture to a temperature at which iron: oup metal and aluminum will readily com ine, cooling nearly to the solidifying point of zinc whereby the aluminum-iron-group alloy will solidify, and thereafter separating the alloy of aluminum and iron-group metal and the zinc fromieach other.

6. The method of removing aluminum and iron-grou' metal from materials containmg' metallic zinc which comprises adding to the molten zinc containing an excess of one of the constituents of iron-group-aluminum alby a materiahcontaining the other constituent of. such alloy, stirring the mass while at a tem rature of at least 500 0., to efiec the com ination of the iron group-' metal with the aluminum, cooling the mixture sufficiently to cause solidification of the alloy of iron-group metal and aluminum but not sufliciently to solidify the zinc, allowing said alloy to rise to the surface of the zinc bath and thereafter separating the alloy of aluminum and iron-group metal,.and the zinc from each other.

7. In the method of claim 1, the step of recovering zinc adhering to the separated allo of iron-group metal and aluminum, whic comprises adding such material to a bath of metal of the iron-group while such bath is at a temperature above the boiling point of zinc, thereby vaporizing the zinc, and collect'ing the volatilized zinc.

8. The method of recovering metallic zinc from admixture with aluminum and a metal of the iron-group which comprises heating the mixture to a temperature at which the aluminum and metal of the iron-group form an alloy, cooling the molten mass to a temperature slightly above the meltin point of zinc until the alloy crystallizes, an separating the molten zinc from the alloy crystals.

9. The method of recovering metallic zinc from admixture with aluminum and a metal of the iron-group which .comprises heating the mixture to a temperature at which the aluminum and metal of the iron-group form an alloy, stirring the molten mass, cooling to a temperature slightly above the melting point of zinc until the alloy crystallizes, and separating the molten zinc from the alloy crystals.

10. The method of recovering metallic zinc from admixture with iron and aluminum which comprises heating the mixture to a temperature at which the iron and aluminum form an alloy, cooling the mass to a temperature slightly above the melting point of zinc to cause the ferro-aluminum alloy to crystallize, and separating the molten zinc from the crystals.

11. The method of recovering metallic zinc from admixture with iron and aluminum which comprises heating the mixture to at least 500 C:, cooling the mass to a molten zlnc.

KARL BORNIEMANN. Vitnesses:

Oscar; F. BROWN, Loms KA'rz. 

